Telephone system.



N. C. SCHELLENGER.

TELEPHONE SYSTEM.

APPLICATION FILED FEB. 24. 1903.

1,147,895. Patented July 27, 1915.

nnwronc. sonnnnnnenn, 0P oHI Ae-o, ILLINOIS, ASSIGNOR roirnnnoee swr'ron BOARD AND sUPPLY COMPANY, or CHICAGO, ILLINOIS, A CORPORATION or ILLINOIS.

TELEPHONE SYSTEM.

Patented July 27, 1915.

Application filed February 24, 1903. Serial No. 144,570.

To all whom it may concern:

Be it known that I, NEWTON O. SOH'EL- LENGER, a citizen of the United States of America, andresiding at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Telephone Systems, of which the following is a specification. i a a My invention relates to telephone systems, particularly of the two-wire typeor those in which the cut-off relays areactuated over circuits involving a portion of the talking circuit. Y a

It has for its main object the provision of a system of the class described in which current is fed from the central battery through the cut-off relay. of the telephone linev and over the line circuit for conversational purposes, whereby there are no leaks or shunts across the line soflthat all current used, except that in the local circuits of the lamps or other signals must-go out over the line. The cut-off relaysact as retardation coils to prevent the short circuiting of the voice currents through the battery.

A further object of my invention is to provide a thoroughly balanced talking circuit when the linesare connected together for conversation,whereby transmission is carried out in the most ,eflicientmanner.

My invention is illustrated in the accompanying drawing in which- Figure 1 represents a diagram of two subscribers lines and a central oilice apparatus for connecting lines together forconversation, and Fig. 2 is a diagram of a slight modification. 1 r

In Fig. 1, L and L indicate subscribers lines extending in two limbs 2and 3 from their'respective' substations A and C tolthe central .oflice. At the substations a transmitter A and receiver 5 are placed in a bridge of the line conductors whose normal discontinuity is maintained by the switchhook 6, a condenser 7 and; hell 8 being located in a permanent bridge of the said conductors. This apparatus is intended to typify any usual or desired common battery outfit. 1

At the central office the line is fitted with an answering jack J and with a plurality of multiple jacks J and J which are normally disconnected from the external line circuit through the contacts of a cut-ofi relay R, the winding of which islegged to ground from the tip conductor of the switchboard section of the said jacks. The line conductor 2 isnormally connected with conductor 9 leading to the line relay R which is grounded upon its other terminal and which controls through its normally open contacts, the local circuit of the individual line signal 5. Line conductor 3 normally connects with a conductor 10 extending to the live pole of the central common battery B.

The operators apparatus comprises a cord circuit havin an answering plug P and a calling plug l provided ,With tip and sleeve contact surfaces adapted to register with the corresponding contacts of the jacks when inserted therein. The tip, contact of plug P is; joined by flexible strand t, condenser c and strand 8 with the sleeve of plug P while the sleeve contact of plug P is united through flexible strand 3, condenser c and strand 6 with the tip of plug P. A supervisory signal S? associated with the answering plug P has its circuit completed from the tip strand 2? over conductor 11 containing resistance 12 and the normal contacts of a supervisory relay 1" which is also connected with the live pole of said battery upon one side, and with the sleeve strand 8 of the cord circuit upon the other side. A similar supervisory signal S is associated with the calling plug P and has its circuit completed through the normal contacts of supervisory relay r and branch conductor 13 containing a resistance 14: and leading to the tip strand t of the cord circuit. The said relay 1' is connected between the live pole of battery B and the sleeve strand 8 of the cord circuit.

The operators head telephone 15, the sec ondary'of her induction coil 16 and a condenser 0 are adapted to be bridged across the calling end of the cord circuit by means of any suitable key, while her transmitter 17 and the primary Winding of her induction coil are included in a local circuit with any suitable source of current, and which may be the battery B. A retardation coil 18 is legged to ground from a point on the operators bridge between the receiver 15 and the secondary winding of her induction coil.

A ringing generator 19 is adapted to be connected between ground and the sleeve contact of calling plug P by the springs 20 of any suitable ringing key while at the same time the tip strand is connected by conductor 21 containing resistance 22 with the live pole ofthe battery B.

In the operation of the system the subscriber A for example takes up hisreceiver and completes a path for current from the battery B over the conductor 10, the sleeve line conductor 3, through the substation instruments and back to the central'oi'hce over line conductor 2 and branch conductor 9 containing line relay R to ground. The current in this path actuates line relay R and the signal S is lighted to indicate the subscribers call. Upon observing the signal the operator inserts the answering plug P in the jack J of the line with the result that current from the battery B is first permitted to flow through lamp S over conductor 11 and through resistance 12, thence over tip strand t and the tip conductor of the jack section of the line and thence through the Winding of cut-ofl relay R toground. The current in this path actuates relay to sever the connection of the line conductors with branch conductors 9 and 10, thus rendering the line signal inoperative and at the same time connecting the external line circuit with the switchboard section. 'As soon as this is accomplished and owing to the. fact that the subscribers telephone is off its hook the path for current from battery B is completed through the supervisory relay 7', over the sleeve strand 8 of the cord circuit, the

sleeve side of the telephone line, through the s ab-station devices, and back to the central oflice over line conductor 2 and thence through the cut-off relay R to ground. The supervisory relay r is actuated by current over this path and serves to open the circuit of supervisory signal S thus rendering the same inert.

The operator connects her telephone with the cord circuit and receives the order from the calling subscriber and then proceeds to test the condition of the wanted line. Normally the testrings of the jacks are insulated from ground and from battery so that no current flows when the tip of a testing plug is touched thereto and the operator knows that the line is idle. As soon as the connection is established, however, the test rings areconnected with the live pole of battery B through the inserted cord circuit, and when the tip of a testing plug is brought into contact with one of said rings a path for current is provided through the operators receiver and the retardation coil 18 to ground causing a click in the operators receiver. She will thus be notified that the line is busy.

Assuming that the line L is found idle the operator inserts the plug P and actuates the ringing key 20. The insertion of the plug operates the cut-off relay over, the con ductor containing supervisory lamp S and the actuation of the ringing key 20 maintains the said relay operated by current over conductor 21, and through resistance 22. The path for ringing current is over the sleeve conductor of the telephone line through the bell at the substation, and thence back tothe central oiiice over the tip side of the lineand through the conductor 21, lead 10, and battery B to ground.

As soon as the subscriber has been called and before his answer the supervisory lamp S is lighted over the path just described including the cut-off relay R. Upon his response the supervisory relay 11 is actuated to render the supervisory signal inoperative and the cut-ofirelay is now energized by the return current over the telephone line as explained with reference to the line L. The subscribersare now in communication and the current from the battery B is fed out through the supervisory relays over the sleeve side of the line with return over the tip sides of the lines and through the cut off relays to ground and thence to the grounded pole of thebattery B. The cutoff relays, as is evident, must presentsuflicient retardation together with that of the supervisory relays to prevent the passage through the battery B of the voice currents. With this arrangement there are no leaks or shunts across the line so that all the battery current except that used in local circuits of the lamps is fed out to the lines.

During conversation it will be noted that owing to the transposed or diagonally connected cord circuit the cut-oil relayslt are legged to ground from the opposite sides of the metallic talking circuit, and that the supervisory relays are connected from the live pole of the battery B- to the opposite sides of the cord circuit. This resultsin a thoroughly balanced talking circuit. A connection from each end of the battery, it will be understood, is thus made to the opposite sides of the metallic talking circuit and upon opposite sides of the condensers interposed in each side of said circuit.

Fig.2 shows a slight modification in that the lamps S and S of Fig. 1 are replaced by the relays r and 1' which controlthe local circuits of the supervisory lamps S and S shown lighted from separate batteries, although the mainbattery B may be and in practice preferably is employed; The relays r and r* are preferable under some conditions of use, such as in connection with very long lines. Y

The several grounds mentioned may and in practice usually are one and the same or they may be the common oifice return.

Various modifications may be made in the details of theinvention without departing from the scope-or principle of the same.

Having thus described my invention what I claim and desire to secure by Letters Patent is A telephone system including telephone lines terminating in two conductor jacks, a central source of battery current, a cut-01f relay for each line having one terminal connected to the tip of the jack and its other terminal connected to a grounded pole of the battery, a link circuit having tip and sleeve talking conductors with interposed condensers uniting the plug terminals thereof, a single-winding supervisory relay for each end of the link circuit having one terminal connected to the sleeve conductor and the other terminal direct to an ungrounded pole of the battery, a supervisory lamp connected through a normally closed contact of each relay between the corresponding tip conductor and the ungrounded pole of the battery whereby when connection is made between a link circuit and a line the cut-off relay is first energized followed by the energization of the supervisory relay and a talking battery supply bridge is provided in which all of the talking current for each line passes through the associated supervisory and cut-off relays.

Signed by me at Chicago, county of Cook, State of Illinois, this 20th day of February 1903.

NEWTON C. SCHELLENGER.

Witnesses:

F. E. JUDsoN, ROBERT LEWIS AMEs.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Fatents, Washington, D. C." 

